The present invention relates to a vertical deflection circuit for use in a display device having a cathode ray tube, and more particularly to a vertical deflection circuit which can shorten a vertical blanking period and is small in power consumption.
In a conventional vertical deflection circuit, as described, for example, on page 157 of a Japanese Publication entitled "Gendai Karah-terebi gijitsu (Modern Television Technology)" edited by Television Technical Committee and published by Ohmusha, a vertical-power-source changeover circuit is used to change the source voltage of the vertical deflection circuit over to a voltage from an additional power source in the vertical blanking period.
Thus, in the prior art, complicated, expensive circuit means is required which supplies electric energy to the vertical deflection circuit in the blanking period, and moreover power loss in a vertical retrace operation is increased. Further, a ratio of the vertical blanking period to a vertical scanning period is as high as about 9%, that is, an effective scanning time is short. Accordingly, it is difficult to increase scanning lines, thereby displaying an image precisely.